Conventionally, there is some demand for low power consumption in active-matrix liquid crystal display devices. One of the known approaches to achieve low power consumption is to perform polarity-inversion drive by changing the potential of a corresponding auxiliary capacitance line after the end of a selection period for each scanning signal line. Such a drive method will be referred to below as a “CS drive method”. The CS drive method allows application of a large voltage to a liquid crystal layer with a small video-signal amplitude, so that power consumption can be reduced. Such a drive method is disclosed in, for example, Patent Document 1.
Furthermore, in recent years, more drivers for driving liquid crystal panels have been formed directly on substrates included in the liquid crystal panels. Examples of such a driver include a gate driver (scanning signal line driver circuit) for driving gate lines (scanning signal lines) and a CS driver (auxiliary capacitance line driver circuit) for driving CS lines (auxiliary capacitance lines as mentioned above). Such a driver is called a “monolithic driver” or suchlike. A liquid crystal display device equipped with such a monolithic driver (referred to below as a “liquid crystal display device with a monolithic driver”) is described in, for example, Patent Document 2. This liquid crystal display device with a monolithic driver renders it possible to achieve a narrow frame region and cost reduction. Conventionally, such a liquid crystal display device with a monolithic driver employs thin-film transistors with amorphous-silicon (a-Si) semiconductor layers (referred to below as “a-Si TFTs”) as drive elements.
Incidentally, Patent Document 3 discloses a drive method for a display device in which a scanning period T1 in which gate lines are scanned is followed by an idle period T2 in which all of the gate lines are not scanned. During the idle period T2, the gate driver is not provided with signals such as clock signals. Accordingly, even when the gate lines are scanned at 60 Hz during the scanning period T1, the total drive frequency for the gate lines can be maintained at about 30 Hz, for example, by setting the idle period T2 to the same length as the scanning period T1. As a result, low power consumption can be achieved.